I

PROCEEDINGS th ANNUAL MEETING THE AMERICAN . . ASSOCIATION OF VETERINARY PARASITOLOGISTS

JULY 18 - 19, 1982

SALT LAKE CITY, UTAH

I PROORJ.\M AMERICAN ASSOCIATICN OF · VE".1'!m1NARY PARASrroux;IsTS ANNUAL MEETJN;

July 18-19, 1982 Ballroom A

SUnday 1 July 18 10:30 Break

SESSICN 1: TREMA'IODES, LITrLE AMERICA 11:00 Control Strategy for Chairmen: D. A. Armstrong and W. J. 7 Fascioliasis Based on Ebryet Seasonal Transmission to Louisiana Cattle 9: 0 0 AM A Feedlot Production Response JB Malone, A Loyacano, M 1 Following the·Removal of F. Hugh-Jones and KC Corkum, Hepatica - Baton R:>uge, IA Ill\ Armstrong, Fort Shaw, Ml' 11 : 15 Dnmunology of 8 hepatica Infect1ons 1n 9: 15 Several Years with RUJmnants 2 Experience GL Zinmerman, Treatment in Corvallis, OR Production-tested Beef Cattle 11:30 Prophylactic Treatment of RE Bradley and RS Sand, 9 Fasciola hepatica in Gainesville, FL Rum1nants R ~w and RH Fetterer, 9:30 Fasciola hepatica in Texas Beltsville, MD 3 Cattle RR Pell, 11:45 Control of Liver FLukes in College Station, 'IX 10 Small KJ Fbryet, Pullman, WA 9:45 Experimental with 4 Fasciola gigantica in Awasi 12:00 Chemotherapy of Sheep 11 JK Kadhim, Baghdad Iraq VJ 'iheodorides, West Chester, PA 10:00 '!he Inp:>rtance of 5 Fascioloides ~ in Wild 12:15 IJJnch ana Ibmesticat.ea" in Minnesota BE Stromberg, SESSICN 2: IMMUNITY, Ballroom A JC Schlotthauer, Chairmen: G. L. Zimnerman PD Karns and GA Conlx>y 1 St. Paul, MN 1:30PM Influence of cell-Mediated 12 Ilmlunity in the Develo:pnent 10:15 A Serologic Survey of of Resistance to Clinical 6 Fasciola hepatica in Coccidiosis in the Chicken Wash1ngton tattle JJ Giambrone and PH Klesius, R3 \'Escott and CJ Farrell, Auburn, AL Pullman, W'A -2-

1:45 Studies on the Active and 1:45 Current Status of Dirofilaria 13 Passive Immunity of Pigs to 18 immitis in Minnesota Migrating Larvae of Ascaris JC Schlotthauer and BE suum Stromberg, St. Paul, MN --m' Rhodes and IA Staudinger, Lincoln, NE 2:00 Periodicity of Dirofilaria 19 tmmitis Microfilariae in Dogs 2:00 Fascioloides Infections in and Mice 14 cattle ~ M1chigan RB Grieve and S Lauria, TW SChillhorn van Veen, Philadelphia, PA East Lansing, MI 2:15 Serology and the Diagnosis of 2:15 Demonstration of a 20 Occult 15 Requirement for Mast Cells in R Scholtens and S Patton, the Rejection of Knoxville, 'IN Nematospiroides dubius from Mice 2:30 Efficacy of Thiacetarsamide r.w Jen and RB Wescott, 21 in Experimentally Infected Pullman, WA Dogs at 2 Months, 4 Months, 6 1'-bnths or 12 1'-bnths 2:30 Reaction of Arteries to POst- with 16 Strongylus vulgaris Larvae Dirofilaria immitis Fbllow1ng Treatment with LS Blair, PF Malatesta, L Ivermectin or Fenbendazole Jacob and DV Ewanciw, 0 Slooombe and BM McCraw, Rahway, NJ Ontario' canada 2:45 PAPER WITHDRAWN 2:45 Isoelectric FOcusing Patterns 17 of Antigens from In Vitro Cultured Cooperia]9unctata GL Z.irmnerman and JE cerro, Corvallis, OR SE leland, Manhattan, KS 3:00 Break 3:00 Break SESSIOO 4: EXPERIMENTAL Sl'ODIES I SESSirn 3: DIROFILARIA, Arizona Rocm Ballroom A Chairmen: R. B. Grieve and B. E. Chairmen: B. Hamnerberg and J. J. Strombetg Giambrone

1 : 30 IM PAPER WITHDRAWN 3:30 PAPER WITHDRAWN -3- 3:45 Factors Contributing to In 3:45 Histologic Findings in Dogs 22 Vitro Development of Ascaris 29 Naturally Infected with suum, from Second-stage Hepatozoon canis Larvae to Adults '1M Cral.g, LP Jones and RM PW D:>uvres and JF Urban, Nordgren, Beltsville, MD College Station, TX

4:00 Sarcocystis as a cause of 4:00 capillaria putorii in 23 Placentitis and Abortion in 30 D:>mestlc cats

Cattle JH Greve 1 Ames 1 IA JP Dubey and JA Bergeron, Bozeman, MT 4:15 Clinical Outbreak of 31 Dictyocaulus arnfieldi in 4:15 Hematologic, Serum Horses 1.n Illl.nol.s 24 Biochemical and Urinary NM Cole, JA DiPietro, GJ Changes in I:X:lgs with Baker, and KS Tcx1d Experimental Dipetalonema urbana, IL reconditum Infections BA Liridemann and JW twt:::Call , 4:30 COmparison of Quantitative Athens, GA 32 Fecal Techniques in Horses JA DiPietro, KS 'Ibdd and 4:30 Stimulation of ~rsecretion NM Cole, Urbana, IL 25 in Stomach Mucosal Cells of Rats b,y In Vitro Products of 4:45 The Population Dynamics of OStertagia Larvae Helminths of the Y Rikihisa and B Hammerberg, Gastrointestinal Tract of Blacksburg, VA Horses at Slaughter

CR Reinemeyer 1 SA. Snith1 RP 4:45 Nutritional and Metabolic Herd and AA Gabel,

26 Effects of Concurrent Col urnbus 1 OH Infections by Coccidia and Nematodes in the Rat 5:00 Experimental Ocular Larva JC Frandsen, Auburn, AL 34 Migrans due to procyonis in SUbl'iuman 5:00 Life Cycle of Isospora suis Prunates 27 in Baby Pigs - KR Ka.zacos, WA vestre and WL Current, JB Ernst and DL FA Kazacos, Lindsay, Auburn, AL West Lafayette, IN 5:30 HOSPITALITY' SESSICN AND SESSICN 5: CLINICAL AND PATHOr.o:;ICAL BUSINESS MEETING, Ballroom A STUDIES, Arizona Roan Chairmen: K. R. Kazacos and T. M. Craig

3:30 Massive Peritoneal 28 Cestodiasis in a I:bg JF Williams, K: Lindsay and ~ .Ehgelkirk, East Lansing, MI -4-

Monday, July 19 11:40 Lunch All Sessions, Ballroom A SESSION 8: REPORl'S 00 SYMPOSIA AND SESSION 6: EP IDEMIOUXiY OF RUMINANTS, IDRKSBOPS Chairmen: R. C. Bergstrom and J. C. Chairman: T. R. Klei Williams

1:00PM : Present State 8:00 AM Corrparison of the 43 of Knowledge and 35 Periparturient Rise {PPR) in Perspectives Fecal Egg Counts of Exotic and JF Williams, D::>mestic Ewes East Lansing, MI CH Courtney 1 CF Parker 1 KE McClure and RP Herd, 1:10 Ostertagia ~rkshop Columbus, OH 44 RP Herd, Columbus, OH

8:15 An Experimental Mcx:lel of 1:20 Dmmunoparasitology Symposium: 36 Breed Resistance to 45 Past Future Haerronchus contortus in sheep GL Zinmerman, CH Courtney, CF Parker, KE Corvallis, OR McClure and RP Herd, Columbus, OH 1:30 Behavioral Cues Which 46 Influence Parasites 8:30 Epidemiology of Bovine ~ Bailey, Auburn, AL 37 I.ungworm Infection in ~stern Range Cattle 1:40 Identification of DE ~r ley, JB Winters, RH 47 Parasites in Tissue Sections: Jacobson and JC Fbx, A New Study Set Available at Bozeman, Mr AFIP CB Gardiner, 8:45 Helminths of Cattle in Washington, DC 38 wyoming: 1961 and 1977 RC Eergstrom and BA Werner, SESSION 9: CHEMOI'HEAAPY-IVERMECTIN Laramie, W'i Chairmen: J. Yaks tis and J. A. Hawkins 9:00 Observation of OStertagia 39 ostert~i Populat1ons 1n Tracer Calves Grazed with 2:00 '!he Effect of Ivermectin on Beef Yearlings 48 Transmission Patterns of JC Williams, JW Knox, KS Equine Intestinal Nematodes Marbury, BA Baumann and 'lG KG Ludwig, '1M Craig and JM Snider, Bossier City, LA Bowen, College Station, TX

9:15 Break 2:15 Efficacy of Ivermectin 49 against Cutaneous in Horses SESSION 7: MINISYMPOSIUM RP Herd and JC Donham, Columbus, OH

9:35 Biology of Cryptosporidiosis 2:30 Ivermectin in Injectable and 40 Cryptosporidiosis Update 50 Paste Formulations: Efficacy oc Anderson, Caldwell, ID against Fourth Stage Strongylus vulgaris Larvae 41 Cryptosporidiosis in Humans ana PostEreatment Responses of and Calves Ponies WL Current, Auburn, AL TR Klei, BJ TOrbet, MR Chap:nan and BS Kramer 1 0: 55 Minor use of Drugs Baton Ibuge, IA 42 WA Knapp, Paleigh, NC -5-

2:45 '!he Efficacy of IVOMEX:: 5:00 Efficacy of Fenbendazole 51 against Dermatobia hominis in 58 against Migrating Ascaris Cattle suum Larvae in Pigs RA Rbncalli and C -r.rB Stewart and TO Binder Benitez-osher, Rahway, NJ Baton Rouge, IA 3:00 Acaricidal activity of 52 Ivermectin against an Experimental Infestation of Psoroptes ovis in Cattle DL Ferguson and TC: Swieczkowski, Lincoln, NE 3:15 Break

SESSION 10: CHEMOTHERAPY Chairmen: v. J. 'Iheodorides and T. B. Stewart

3:45 Cestocidal Activity of 53 Fenbendazole in Calves H Ciordia, JA Stuedemann and HC rvteampbell, Experiment, GA.

4:00 Clinical Trials with 54 Combinations of Mebendazole and Piperazine in Horses JA DiPietro, A Paul and KS 'Ibdd, Urbana, IL 4: 15 Prophylaxis of Porcine 55 Cbccidiosis with salinomycin TJ Kennedy and JE Shively, Terre Haute, IN 4:30 Significance of Parasite 56 Stage on Perceived Anthelmintic Efficacy against Infection in Dogs TA Miller, Kansas City, KS 4:45 The Effect of Xanthene Dyes 57 on Bovine Gastrointestinal Nematodes JA Hc:twkins , JR Heitz and M: Healey and MH Johnson Mississippi State, MS -6-

1 A FEEDwr PRODUCI'ION RESPONSE FOI..LCWI!.'K; '!HE REMOVAL OF FASCIOIA HEPATICA D. A. ARMSTRONG, Fort Shaw, M:>ntana.

Although liver flukes are a cause of serious economic 1oss in cattle, in the past many of these losses have been fXX>rly defined. Such losses include reduced average daily gain, increased feed r=er gain, lowered fertility, reduced mature b:xly weight, and lowered weaning weight. 'nlis paper will discuss some of the practical information that has been gathered on the economic impact of bovine fascioliasis. Feedlot managers who deal with fluke-infected cattle report a C'Oil1l'On experience. Such cattle usually gain and convert as anticipated until the final stages of finishing. At this point, a dramatic reduction in growth and feed efficiency occurs, resulting in protracted, costly losses. In one Oklahoma feedlot, we analyzed production records to o:::>rnpare fluke-infected cattle with cattle that were uninfected. 'nle infected cattle demonstrated consistently lower average daily gain, higher feed conversion ratios, and higher cost of gain. Steers subsequently treated for fluke infection gained nore weight and had fewer livers condemned at slaughter than untreated steers. Additional research is needed to adequately characterize the economic significance of fascioliasis in cattle production.

2 SEVERAL YEARS' EXPERIENCE WI'IH FASCIOIA HEPATICA 'l'REA'I'MENr IN PRODUCTION TESTED BEEF CA'ITLE R. E. Bradley and R. s. Sand, College of Veterinary Medicine, University of Florida, Gainesville, Florida.

'nlis study was started in 1977 to determine if albendazole (ABZ) was as effective as hexachlorethane (HEX) in controlling infection in a practical production situation in Florida. Approximately 100 Aberdeen-Angus heifer calves fran the herd were divided into 2 groups: an ABZ-treated group and a HEX-treated group. Treatment was at 3 to 6 months of age and then at 6 to 8 month intervals until their first calves were weaned at 3 years of age. 'nlis was repeated in 1978 arrl 1979. From the 3 years of calf crops, the average fertility rate for the ABZ-treated group was 92.5% and for the HEX-treated group 87.5%. 'nle calf weaning weight for the ABZ-treated group has been significantly higher (p>.OS) than for the HEX-group. 'nle difference was 6. 9 kg ( 15 lbs.) when adjusted to the standard 205 day age. It was concluded that ABZ treatment of cows twice anually resulted in a significant improvement of calf weaning weights as compared with HEX treated cows.

3 FASCIOIA HEPATICA IN TEXAS CATI'LE R. R. BEIL, Department of Microbiology and Parasitology, College of Veterinary Medicine, Texas A&M University, College Station, Texas.

Feeder steers free of F. hepatica were used to determine economic loss due to F. hepatica under fUll feed conditions. Ten steers were infected with metacercar~ae and ten used as controls. 'nle animals were housed -7-

individually and daily feed was "Weighed. '!here were no differences in weight gains or feed efficiency. A large herd of purebred cattle is being used in a field trial. All animals have been treated with albendazole in the spring and fall for 5 treatments and all indicators show reduced numbers, and effects from flukes have been reduced.

4 EXPERIMENTAL INFECTIONS WITH FASCIOIA GIGA.NTICA IN AWASI SHEEP J. K. KADHIM, Veterinary Ial:x)ratorJ.es and Research Institute, Abu Ghraib, Baghdad, Iraq.

Six lambs, 3-4 roonths of age, which had not previously been exposed to Fasciola gigantica infection, "Were each infected artificially with a single dose of 200 metacercariae of Fasciola gigantica. The experimental infections "Were studied over a peri@ of 22 weeks. A group of 6 noninfected lambs served as controls. All infected lambs showed signs which could be attributed to fascioliasis. '!he eggs "Were for the first time detected in the feces of all infected lambs from 99-108 days postinfection; the number of flukes recovered varied from 36-76, the rrean fluke burden being 54.5. There was an increase in the serum gamna globulin of 39% during the first 18 weeks after initial infection. Ebsinophilia was observed at 2-4 weeks postinfection, and later, there was 'Well-marked anemia. '!here appeared to be no direct relationship between the garrma concentration and eosinophilia.

5 'IHE IMPORI'ANCE OF FASCIOIDIDES MAGNA IN WILD AND OOMESTICATED ANIMALS IN MINNESOI'A B. E. S'I'K>MBERG, J. C. SCHLCYI'I'HAUER, P. D. KARNS and G. A. CONBOY, Department of veterinary Pathobiology, College of Veterinacy Medicine, University of Minnesota, St. Paul, Minnesota, and Forest Wildlife and Populations Groups, Minnesota Department of Natural Resources, Grand Fapids, Minnesota.

White-tailed deer, O:Jocoileus virginianus, the definitive oost for the liver fluke , are foili'id throughout Minnesota. In the traditional range of the Northern half of Minnesota, deer population densities vary from 75 per square mile in a state park, to 1 per square mile in the nore agricultural areas. The infection rate was estimated at 68.8% in 1952, 46% in 1960, and varies between 10 and 53%, in 1981, depending on the area. 'Ihe deer population overlaps with the state's noose (Alces americana) population in the northeast and northwest corners of the state. ihe infection rate in noose, as determined by carcass examination during the noose hunting seasons, over the last eight years ( 1973, 1975, 1977, 1979) was 12.8% (118 of 920) in the northeast region. Here the ranges of the two species overlap only in the southern noose range near Lake Superior. Liver fluke infection in noose is not a definitive for this trematode. In the northwest corner of the state where ooth populations overlap throughout the noose range, the infection rate is 64.5% ( 1120 of 1736) and infected animals are found throughout the area. 'Ihe -8-

most intensive sheep raising occurs in this northwest corner where much of the land is agricultural. Practitioners report that this area and most of the northern tier counties have endemic F. ~a which causes major problems for the sheep producer. 'Ihese findings ~cate the need for good pasture management in the areas where sheep and deer populations ~erlap.

6 A SEROLOOIC SURVEY FOR FASCIOLA. HEPATICA IN WASHm:;'ICN CA'ITLE R. B. WESCOIT and C. J. FARRELL, Department of Microbiology and Pathology, College of Veterinary Medicine, washington State University, Pullman, Washington.

Sera from 100 herds of cattle were examined with an enzyme-linked inmunosorbent assay {ELISA) for antibody to Fasciola hepatica in a preliminary screening involving 5 to 10 samples per herd. '!he results suggested that 28 herds contained infected cattle and that the parasite was most prevalent in three distinct geographic areas. Subsequent retesting of all sera available from 14 representative herds {mean of 109 samples for each) indicated that the screening test detected 7 of 7 operations in which approximately 50% of the cattle had positive or suspect titers and 3 of 4 operations in which approximately 10% of the cattle had positive or suspect titers. cne of three herds considered negative on screening had a few {7%) samples with suspect titers. Accuracy of ELISA also was compared to diagnosis of F. hepatica by the fecal sedimentation technique in these same herds. A gcx:Xl correlation ( 5 of 5) was found where a high percentage {50%) of sera were positive or suspect. NO Fasciola eggs were found in samples from tw.:> herds with 10% positive or suspect sera an::'i two herds that were negative by ELISA.

7 CCNrROL STRATF.X;Y FOR FASCIOLIASIS Bl\SED CN SEASONAL TRANSMISSION 'ID LOUISIANA CA'ITLE J. B. MAtDNE, A. JJJYA.CM:\K), M. HUGH-JOOES and K. C. CDRKUM, I.Duisiana State University, Baton Pouge, I.Duisiana.

'!he effectiveness of albendazole (ABZ} against Fasciola hepatica in cattle was studied in relation to a 3-year seasonal transm~ss~on study. Methods involved correlation of treatment time to data on sentinel calves, quarterly herd infection prevalence, and bi-weekly snail population studies. '!he number of flukes found in 4-6 sentinel calves was 13 in 1979 {mid-May to July grazing period}, 456 in 1980 {late February to July}, an::'i 22 in 1981 {late February to July). Yearly variation was related to the suitability of snail habitat microclimate. Herd treatment in October with ABZ reduced herd prevalence and mean epg counts 3-4 months later from 42% {0.9 epg) to 31% (0.6 epg) in 1979-80 and from 96% (13.7 epg} to 38% (1.0 epg} in 1980-81. Treatment with ABZ in 4 other herds in the coastal marsh region resulted in a reduction in herd F. hepatica prevalence from 88-93% (4.2-16.2 epg} in August-NOvember, 1980 to 16-57% (0.2-1.9 epg} in March-June, 1981. Herd prevalence and epg values remained relatively stable through the fall of 1981 whether herds received one, tw.:> or no additional ABZ treatments in the winter, spring and summer. Seasonal -9-

transmission data indicated that 1981 was a "low-risk" year for fascioliasis. Herd performance testing in one of the 4 herds in 1979 through 1980 revealed a 10. 1 kg advantage in 205-day adjusted weaning weight and a higher grade ( 11 vs 9) for calves fran 41 cows treated with ABZ in June 1979 and February 1980 as compared to calves fran 41 cows treated with levamisole on the same dates. Group infection prevalence was reduced from 70% (5.8 ep;J) to 67% (2.0 epg) 3 :rronths after ABZ treatment in July 1979, and from 9 5% ( 15. 4 epg) to 44% ( 1 • 3 epg) 2 :rronths after ABZ treatment in February 1980.. In the levamisole treated group, prevalence was 36% ( 4. 2 ep;J), 80% (12.1 ep;J), 95% (19.3 epg) and 75% (8.6 epg) in July and September, 1979 and February and April, 1980, respectively. seasonal transmission data indicated 1980 was a "high-risk'' year. Results suggest that ABZ is rrost effective in the fall when rrost flukes are mature and less effective in the spring-early sumner when a mixed mature-immature p:>pulation is present. A control strategy will be prop:>sed based on F. hepatica seasonal transmission patterns, available flukecides, management factors, and cost-effectiveness.

8 IMmNOI.DGY OF FASCIOIA HEPATICA INFECTIONS rn RUMINANl'S G. L. ZIMMERMAN, Sdh051 of Veterinary Medicine, Oregon State University, Corvallis, Oregon.

'nlis presentation will be a review and update of the knowledge about the -liver fluke imnune interface. 'Ibpics to be addressed will include the following: 1) comparisons and contrasts of the immune interactions between liver flukes and either sheep or cattle; 2) stimulation of the ruminant inmune system by F. hepatica; 3) avoidance, modulation, and suppression of oost irmlune systems "EY F. nepatica; and 4) research leading to the ~rotection of ruminants against!· hepatica.

9 PROPHYlACTIC TREATMEN1' OF FASCIOIA HEPATICA rn RUMINANI'S R. s. REW and R. H. FE:rl'ERER, Aruma! Paras1.tology Institute, Agricultural Research service, u. s. Department of Agriculture, Beltsville, Maryland. Controlled-release administration of anthelmintics through implanted capsules or intraruminal boluses seems to offer an effective alternative to conventional treatment regimens. 'nlese delivery systems should provide several advantages to present day regimens by: 1) Acting prophylactically against helminth parasites :im:nediately upon entry to the oost to prevent pathology of larval stages and interrupt the life cycle of the parasite; 2) decrease handling costs by reducing number of treatments; and, 3) increase safety by decreasing potential toxicity to large, single roses. With these goals in mind, "We selected a series of oompounds reported to be effective against Fasciola hepatica, the common liver fluke, as a single oral rose to determine their proPhylactic efficacy and pharmacokinetic properties under simulated o:mtrolled-release conditions in sheep and calves. 'nle four com,pounds chosen were: 1) Diamfenetide, 2) albendazole, 3) MK-401, and 4) closantel. Diamfenetide given orally at 7.5 m;/kg/day for 21 or 28 days proved to be 93-97% effective in preventing F. hepatica infections in -10-

sheep, but required 30 mgjkg/day for 28 days to l:::e 88% effective in cattle. Albendazole given at 3 mgjkgjday for 28 days was 98% effective in sheep, but was without efficacy in calves even at 5 mgjkgjday. MK-401 at 3. 5 mgjkgjday for 28 days was 62% effective in sheep arrl is presently l:::eing tested in calves. Closantel at 10 mgjkg given subcutaneously was 44% effective 2 wks after and 52% effective 4 wks after a single injection in sheep. Trials are presently underway with t'WO injections of 10 mgjkg spaced 4 wks apart in sheep. 'Ihe daily oosage provided an advantage by increasing time of protection frcm 1 day to 1 rronth with little increase in amount of total drug or provided a new type of activity. Pharmacokinetic data for serum levels of these anthelmintics gave additional information about the efficacy properties of these anthelmintics. Diamfenetide reached a peak of 9. 1 I'lll'Oles/ml 4 hrs after treatment and returned to 2. 5 llil'Oles/mg by 24 hrs in sheep serum. Albendazole was not recoverable in the serum, but two major metabolites a sulfoxide and a sulfone were present for 48 hrs. Marriner and Bogan reported that the sulfoxide was the active metabolite. We found that the sulfoxide rretabolite was found in 2X higher concentration in sheep serum than calf serum, while the sulfone metabolite anounts were reversed, 2X rrore in calf serum at 24 hrs. Closantel turned CNer very slowly with half-time turnover of 5-6 wks for a single subcutaneous injection.

10 CONTROL OF LIVER FWKES IN SMALL RUMINAN'1S W. J. FOREYT, Department of Veterinary Microbiology and Pathology, Washington State university, Pullman, Washington.

Fasciola hepatica and Fascioloides magna are t'WO liver flukes that occur COOill6rily in srnail rum1nants m North America. Fasciola hepatica is found frequently in sheep and goats and is generally restr1cted to the liver. Fascioloides magna is also found in sheep and g::>ats in areas where wild cervid hOsts are mfected. Infection in sheep and goats usually results in 100% rrortality within 6 months of infection. Migration of irrmature F. magna in these hosts is often unrestricted, and flukes can l:::e recovered-frcm organs other than liver. Albendazole at 15- 30n:gjkg of tody weight was effective against either fluke in small ruminants. Early treatment of small ruminants infected with F. magna is essential.

11 CHEM>THERAPY OF DICRCCOELIUM DENDRITICUM v. J. 'IHEX)[X)RIOES, SnitfiKline Ariliiiai Health PrOOucts, 1600 Paoli Pike, West Olester, Pennsylvania. Dicrocoelium dendriticum, a three-host fluke, is a common parasite of ruminants m 011erseas 1 countries and in a few states in the U.S. and Canada. 'Ihe dlenotherapy of this fluke !::egan b:.tck in 1936 with fuadin. In 1947, hexachloroethane and, in 1948, carbon tetrachloride were given to infected sheep. All of these drugs showed very little activity against D. dendriticum. Hetol and hitolin were used with low to ncderate success. -A s1ngle dOse of 150 - 300 mg/kg of thial::endazole eliminated 99.5% of the flukes. cambendazole at 240 - 300 mgjkg afforded tetter than 90% 'WOrm -11-

reduction. Diamphenethide at a dose level of 240 rngjkg showed 98% efficacy. Fenbendazole at 20 mgfhg per day for 5 days or a single dose of 100 - 150 rngjkg was found to te highly efficacious. Praziquantel 50 mgjkg reroc>ved 92% of the flukes. Several studies dem::>nstrated that albendazole as a single dose of 10 - 20 mgjkg afforded extremely high efficacy. It was also rep:>rted that albendazole, two doses of 7.5 mgjkg given seven days apart, eliminated 92% of the fluke burden.

12 INFWENCE OF CELL-MEDIATED IMMUNITY IN THE DEVELOPMENT OF RESISTANCE 'ro CLINICAL CCX:CIDIOSIS IN 'lEE CHICKEN J. J. GIAMBRONE, Poultry Science Department, Auburn University, and P. H. KLESIUS, USDA, ARS, Regional Parasite Research Laboratory, Auburn, Alabama.

Four compounds, previously shown to stimulate irrmunity, -were examined for their ability to modulate the chickens' immune resp:>nse to coccidiosis vaccination. 'lhe following four compounds levamisole, CP20,960' Bordetella bronchiseptica bacterin, and a dialyzable leukocyte extract conta1n1ng transter factor were given to 1-week-old broilers at the time of coccidiosis Unmunization. Three weeks later the birds were challenged and various performance parameters determined. All four compounds were found to p:>tentiate the immune response to coccidiosis vaccination as measured by percent livability, percent weight gain, and fecal score during a 7-day challenge period. In addition, three of the compounds were found to alleviate the adverse depression in weight gain 'Which initially followed coccidiosis vaccination. The results suggest that irrmunop:>tentiation of coccidia vaccination is p:>ssible and may te helpful in the prophylactic control of coccidiosis.

13 STUDIES CN 'lHE ACriVE AND PASSIVE IMMUNITY OF PIGS 'IO MIGRATI'I'l3 LARVAE OF ASCARIS SUUM M. B. :moDES and L. A. SI'AUD!l'l3ER, Department of Veterinary Science, University of Nebraska, Lincoln, Nebraska.

Fbur separate procedures were used to determine their respective effectiveness in increasing the resistance of pigs to migrating larvae of Ascaris suum. Active immunity stimulated by perienteric fluid of A. suum, non-specilic i.mnunity by prior infection of pigs with tra.nsiDisSI'Ere gastroenteritis virus ('!GE), t=assive transfer of immune sera, or t=assive transfer of lymphocyte lysates (transfer factor) all failed to increase the resistance of pigs to migrating larvae of A. suum. J?erienteric fluid stimulated an antil:cdy and cell mediated inmune resp:)nse. Passive transfer of sera resulted in a greater number of superficial liver lesions and an increased resistance of the livers to a puncture probe o:mpared to those from control animal. Skin tests for delayed hypersensitivity for pigs receiving lymphocyte lysate {prepared from immune or: control pigs] were negative for all pigs. 'lhe eosinophil counts in the blocx:l of the animals immunized with perienteric fluid, pre-infected with TGE virus or controls were similar at necropsy which was 8 days after oral challenge with embryonated eggs. -12-

14 FASCIOLOIDES INFEcriONS IN CATI'LE IN MICHIGAN T. W. SCHILLIDRN VAA VEEN, Department of large Animal Surgery and Medicine, Michigan State University, East Lansing, Michigan.

Fascioloides magna is the only liver fluke indigenous to the Great Lakes reg1on. 'Ihe mal.n reservoir hosts are White-Tailed r:eer, of which up to 32% -were found infected in the northern parts of Michigan. A survey on the prevalence of detectable liver fluke infection in slaughtered cattle revealed that during 1978-1980, 0.65% of the livers of 1.4 million slaughtered cattle were condemned. The condemnation rate was 0.4, 3. 7, and 13.9% in cattle from Michigan's Lower, northern Lower and Upper Penisula, repectively. Many slaughtered cattle in southern Michigan were imported from other states, however. The highest oondemnation rate was recorded from Chippewa oounty. 'Ihere was little evidence of a seasonal variation in the oondemnation rate~ outbreaks of clinical disease were nnst

15 DEMO\ISTRATION OF A RECUIREMENT FOR MAST CELLS IN 'IHE REJEX:TION OF NEMA'IDSPIROIDES DUBIUS FRCM MICE L. W. JEN arid R. B. WEScOTT, Department of Microbiology and Pathology, College of veterinary Medicine, Washington State University, Pullman, Washington.

Rejection of Nematospiroides dubius was examined and a:xrtpared in :rrast cell deficient mice (Wj'WV), noiinal mice of the same strain (+/+), c57 inbreds which were the foundation stock for both W/W' and +/+, and random bred Swiss-Webster mice (SW). In initial experiments 250 N. dubius larvae, administered orally 3 times at 1 or 2 week intervals, were shOWh tO elicit a pronounced "self cure11 in SW but not in W/VI" mice. Subsequent experiments revealed that rejection also did not occur in +/+ or C57 hosts. Hence our preliminar.y conclusion that lack of mast cells in the W/VI" hosts was responsible for failure to reject was incorrect. Presently it appears that the C~7 host lacks some factor or factors, as yet unidentified, needed for reJection of N. dubius and that this same unresponsiveness is characteristic for W/VI" and +/+ mice.

16 REACTICN OF ARl'ERIES '10 STRONGY'WS VUI..GARIS LARVAE FO~ TREATMENI' WITH IVERMECTIN OR FENBENDAZOLE 0. SLOOOMBE and B. M. MCCRAW, Department of Pathology, University of Guelph, Guelph, Ontario, canada, N1G, 2W1.

Shetland-cross ]?Ony foals, 6-1 0 -weeks of age and reared worm free from birth, were infected with infective Strongylus vulgaris larvae and 56 days after infection were given either ivermectl.n intramuscularly at 200 ugjkg body weight or fenbendazole via stomach tube at 50 mgjkg for 3 days or 10 mg/kg for 5 days. 'Ihe two anthelmintics were used in separate studies and in each of these there were infected and untreated foals. Examination of the treated foals at necropsy 35 days after treatment revealed a resolving arteritis and minimal thrombosis. Ivermectin and fenbendazole were highly effective in eliminating later 4th-stage larvae fran the lumen of the cranial mesenteric artery and its branches. -13- 'Ihe ileocolic artery of these foals was examined histologically and larvae were found relatively deep in the wall of the artery in the i vermectin-treated foals and close to the intima and in thrombi in the fenbendazole-treated foals. Many larvae were found in the former and these appeared intact, but viability was difficult to determine. In the latter, only severely disrupted larvae were observed. 'Ihe intima in J:::oth groups was discontinuous and the tunica media several times normal thickness. There was infiltration of eosinophils and mononuclear cells and deposits of hemosiderin and this was more extensive in the fenbendazole-treated foals.

17 ISOELECTIC FOOJS:n:G PATrERNS OF ANTIGENS F!Ot IN VITRO CULTURED COOPERIA PUNCI'ATA ~ and J. E. CE:R:f(), School of Veterinary Medicine, Oregon State University, Corvallis, Oregon and s. E. LElAND, JR., Department of Lab::>ratory Medicine, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas Cooperia punctata were cultured in vitro for 21 days with resulting worm populations cons~sting mainly of aaults, same fourth-stage, and a few third-stage larvae. Excretory-secretory prcducts {ESP) greater than 10, 000 daltons were recovered by Amicon ultrafiltration from balanced salt solutions-antibiotics {BSSA) in which these ~rms had been incubated for 48 hours. Prior to lyophilization, BSSA was exchanged with either distilled water {Kansas) or phosphate buffered saline {Oregon) • Protein concentration of ESP prepared by the Oregon procedure averaged 4. 06 x 1 o-9 g/~rm whereas by the Kansas method, the average protein content per ~rrn was 2. 97 x lo-9 g. ESP were separated by analytical flat-bed isoelectric focusing using pre-prepared polyacrylamide-ampholyte gels {LKB) of a 3-9 pH range. r.t:>re than 42 bands were resolved in each preparation. Separation patterns of both preparations were similar except that a particular band at pH 7. 2 was rore intense in the Kansas ESP than in the Oregan ESP.

18 CtJRRENr STATUS OF DIOOFIIARIA IMMITIS IN MINNESOTA J. c. SCHI.Ol'rHAUER and B. E. S'I'RCM3ERG, Department of Veterinary Pathobiology, University of Minnesota, St. Paul, Minnesota.

Endemic canine heart\\'Orm, Dirofilaria i.rrmitis, infection was observed in east central Minnesota as early as 1937. Epizootic canine dirofilariasis was first encountered in Hennepin County, which contains the city of Minneatx>lis, in 1956. Since that time, the parasite has oontinued to spread al'OC)ng Cbgs and by 1980 had become endemic in 30 of Minnesota's 87 counties {5 counties in 1960, 25 counties in 1977) • Although the pa.rasi te continues to expand its range within the state, the m.nnber of new animal infections has been shown to fluctuate and probably reflects; 1) rainfall and subsequent mosquito density, and 2) the prevalence of diethylcarbamazine preventive therapy in dogs. Recent mail surveys anong Minnesota veterinarians revealed 2180 ( 4. 1%) D. imnitis infections annng 53,770 dogs tested in 1976, 1383 (2.1%) infect~ons annng 64, 671 dogs tested in 1977, and 899 ( 1 • 1%) infections arrong 81 ,075 dogs tested in 1980. Heart~rm is primarily an infection of dogs, but is also seen in cats, red foxes and coyotes. 'Ihe 10 counties with the largest number of new canine heartworm infections in 1980 were, in order of occurrence, Hennepin, Anoka, Ramsey, Dakota, Blue Earth, carver, Chisago, Washington, Isanti and Crow Wing. -14-

19 PERIODICITY OF DIROFILARIA IMMITIS IN DOGS AND MICE R. B. GRIEVE and s. LAURIA, Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.

Cell-free microfilariae of Dirofilaria immitis were recovered from an experimentally infected 00g and inoculated intravenously into adult female BALB/c mice. Each rrouse received 1 x 105 microfilariae. In one experiment mice were bled and microfilariae were oounted 7, 14 and 21 days after inoculation at roth 1100 and 2300 h. A similar experiment was conducted with mice that had received 550 R gamma radiation 24 h prior to inoculation; microfilariae were oounted at 1100 and 2300 h 7, 14, 21 , 28, 35 and 42 days after inoculation and bled at 4-h intervals for 48 h; microfilaria numbers at each bleeding were compared to numbers of microfilariae present at the same time in the d::mor Cbg. In a fourth experiment 2 groups of mice were irradiated, inoculated and bled as before; one group was acclimated to light from 0700 to 1900 h whereas the other group was acclimated to light from 1900 to 0700 h. 'Ihe microfilaremia was subperiodic, varying regularly with time in roth the d:>g and mice. Microfilariae in the 00g reached maximum numbers during light hours. In each experiment, regardless of actual time, rnicrofilariae in mice reached maximum numbers during dark hours. These data suggest that the extent of microfilaremia may re directly related to the level of activity of the host. (NIH Research Grant AI-18249).

20 SEROI.CGY AND THE DIAGNOSIS OF OCCULT DIROFILARIASIS R. SCHOLTENS and S. PAT'!ON, Department of Pathobiology, College of Veterinary Medicine, University of Tennessee, Knoxville, Tennessee.

An ELISA test for d:>g heartl'.Onns was evaluated in a p:>pulation of normally exp:>sed d:>gs. After categorization based on rredical histories, clinical examinations, Knott's tests and thoracic radiographs, antibody was found to re present at relatively lOW titers in non-infected OOgS (mean = 30), dogs with patent heart"WOrm infections (mean = 122), and d:>gs with previous heartwonns infections (mean= 64), while high levels of antibody (mean = 2896) were found in d:>gs with occult dirofilariasis. There is g:x::ld evidence that true occult dirofilariasis is an immune-mediated rondi tion characterized by very high levels of hum:::>ral antibody, and that it is sometimes oonfused with long-standing semi-patent or previous heartl'.Orm infections recause of similar clinical signs and radiographic evidence.

21 EFFICACY OF THIACETARSAMIDE IN EXPERIMENTALLY INFECTED rxx;s Nr 2 MONTHS, 4 M:NrHS, 6 ~, OR 12 MONTHS IOSTINFECTICN WITH DIROFII.ARIA IMMITIS. L. s. BIAIR, P. F. MALATESTA, L. JACOB, and D. V. EW'ANCIW, MerCk Sfia:rp & Ibhrne Research Laboratories, Rahway, New Jersey.

The activity of thiacetarsamide against experimental infections of Dirofilaria inmitis in male reagles was studied in a time dependent fashion. 'Ihe standard thiacetarsamide regimen ( 2 consecutive days of morning and afternoon dosing of commercial thiaoetarsamide sodium solution [ 10 mg thiacetarsamide sodium/rnl] given intravenously at 0.1 rnl per p:>und -15-

of b:xly ....-eight) was given 2 months, 4 months, 6 months, or 12 months postinoculation to groups of 5 dogs. Two groups of controls received no treatment. Che control group was necropsied 8 weeks after the 6-months treatment time, together with the first three treatment groups. The other control group was necropsied with the group treated 12 rronths postinoculation approximately 8 ...... eeks after that treatment • W:Jnn burdens for the two sets of controls were similar (x = 59 + 3.2 standard error, x = 51 + 7.2). The drug was rrost effective when given 2 months p:>stinfection believed to be before the time at which wonns migrate to the heart {X = Q. 2 + 0.2). Treatment was least effective when given 4 months p:>stinfection, a time thought to correspond to early arrival in the heart (x = 41 + 8.0). No differences in wonn burdens were seen between dogs treated at s-months {presumed to have young adult wonns) (x = 20 + 3.3) and those treated at 12 months (presumed to have mature heartworm) (x = 19 + 5.1). Wy 1 of the 10 dogs treated at 6 or 12 months p:>stinfection was negative for adult heartv.onn at necropsy but 8 of the 10 had only female worms.

22 FAC'IDF.S CONTRIBUTIN.; 'IO rn VITFO DEVEI.DPMENT OF ASCARIS StruM, FROM SECCND-STAGE I.ARVAE 'IO ADULTS - F. w. DOUVRES and J. F. URBAN, JR., Animal Parasitology Institute, Agricultural Research Service, u. s. Department of Agriculture, Beltsville, Maryland

second-stage larvae of Ascaris suum, artifically hatched from eggs, have been grown in vitro to young ad~males and to mature females mich laid unfertilized eggs. These developnental stages were obtained in a three-step roller culture system which consists of (1) medium KW-2 supplemented with 10 mM L-cysteine for the first 4 days and 5 mM for the following 7 days; ( 2) followed by medium API -18 for 7 days; and ( 3) thereafter, by medium API-1 supplemented with a t:ovine hemin canpound at a concentration of 24 mcg/ml. CUltures were gassed with 95% nitrogen/5% carbon dioxide for the first 4 days and 85% ni trogen/5% oxygen/10% carbon dioxide, thereafter; and incubated at 39 c. Beginning with inocula of 300,000 to 600, 000 larvae, this system producted maximal yields of 90% early to late third stage by day 11, 1 to 50% fourth stage by 18 to 25 days, and less than 1% that advanced through fourth nolt to mature crlults by 30 to 166 days. A. suum larvae developed to young crlult males and females, with t:x:xly lengthS'OT 14 to 28 mm, as early as 34 to 38 days; and to egg-laying mature females, with 't::ody lengths of 80 to 85 mm, as early as 67 to 73 days. Thus far, the largest young adult male neasured 47 mm long and the largest mature female neasured 95 mm long. In one trial, between days 73 to 166, a mature female 011iposited about 97,000 unfertilized eggs that were encased by the shell and a refractive, manmilated albuminous coat.

23 SARCOCYSTIS l>S A CAUSE OF PLACENTITIS AND ABORTION IN CA'I'l'LE J. P. OOBEYl and J. A. BERGERON2, veterinary :Research Laboratory, Department of Veterinary Science, !Vbntana State University, Bozeman, r.t>ntana 1, and De~rtment of Livestock, Diagnostic Laboratory Bureau, Bozeman, r.t>ntana •

An crlul t, multiparous Hereford cow from Frenchtown, r.t>ntana, aborted a near-tenn female calf. The aborting cow was clinically nonnal. Multiple -16-

foci of necrosis were seen in the placenta, mainly involving lamina propria. 'Ihere was a mild polymorphonuclear leukocyte arrl a rrononuclear cell infiltrate in the lamina propria of cotyledonary villi and an increase in rnacrophages in the deeper villar portion of lamina propria. Focal mononuclear cell infiltrates and necrosis were present in glomeruli and in intertubular connective tissue in cortex and renal medulla. Lungs were edematous, congested, and there were focal interlobular heiTOrrhages arrl focal vasculitis. Meronts of Sarcocystis in all stages of developnent, were found in endothelial cells ot capillaries, arterioles, and arteries of placenta, fetal lung, and kidney. 'Ihe meronts were structually identical to those of coyote-derived Sarcocystis cruzi.

24 HEMA'ror..a;IC, SERUM BIOCHEMICAL, AND URINARY CHAJ::X;ES IN lXGS WITH EXPERIMENTAL DIPETAI.DNEMA RECONDITUM INFECTIONS B. A. LINDEMANN, J. W. MCCALL and T. L. EVANS, Department of Parasitology, College of Veterinary Medicine, 'Ihe University of Georgia, Athens, Georgia.

Di:e;talonerna recondi tum is known to :parasitize Cbgs in the United States, but its role as a canine :pathogen has been largely ignored. Therefore, the present study was initiated to characterize cellular, serum biochemical, and renal responses in dogs with experimental dipetalonerniasis and in dogs with existing dlronic experimental infections. All Cbgs were microfilariae negative prior to inoculation and protected from rrosqui toes and fleas. For experimental infections, three male arrl three female Beagles, six to seven ronths of age, -were subcutaneously inoculated with 30 infective larvae per dog. A duplicate group of Beagles served as uninfected controls. Mean values for total RBC, HB, PCV, K:H, K:V, total and differential WBC, Knott's tests and weights were compared preinoculation and weekly thereafter. 'lbtal protein, albumin, BUN, ALT and CK were compared preinoculation and biweekly thereafter. Routine urinalyses and fecal exams were performed preinoculation and 28 weeks postinoculation. Mean total WBC were significantly {P<0.05) greater in infected Cbgs than in uninfected Cbgs 4, 5 and 7-12 weeks PI. Mean eosinphil counts were signficantly greater in infected dogs than in uninfected dogs 3-11 , 13-15, 20, 23 and 24 weeks PI. Basophils were detected only in infected cbgs 13, 15, 16 and 18-20 weeks PI. Microfilariae were detected 10 weeks PI and sporadically thereafter in three infected dogs. Mean values for remaining tests were not significantly different. One infected female developed a subacute purulent lymphadenitis of undetermined origin 17 weeks PI and was subsequently deleted from the study. Six wurrns were recovered at necropsy 18 weeks PI. All remaining infected ebgs were necropsied 28 weeks PI and a total of one adult YDrm was recovered. Four of five dogs with chronic infections {70-89 weeks PI) has eosinophilia ( 1046-3690), one of five had lymphocytosis ( 5170) and three of four dogs examined had proteinuria ( 30+ to 100+ ng/dl). -17-

25 sriMUI..ATION OF HYPERSECRETION IN S'IOMACH MUCOSAL CELLS OF RATS BY IN VITRO PRODUCTS OF OSTERT.AGIA LARVAE Y. RIKIHISA and B. HAMMERBERG, College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia.

Infection of n.nninant abomasa by OStertagia results in mucous cell hyperplasia and decreased acid secretion. smail molecular weight peptides (G-25II) which inhibit respiration of isolated gastric glands have t:een isolated from in vitro products of Ostertagia. 'll'le _!!! .~ ef.fects of G-25II on rat stomachs are rei,X>rted here. Rats were 1ntraper1toneally injected wit.'f-t 2 ng of G-25II twice a day for 3 days. As a control, the same preparation from the culture medium without Ostertagia was intraperitoneally injected into rats on the same schedule. The rats were starved 24 hours after the last administration, then sacrificed. The stomach was cut out and imnersed in fixatives after intralumenal fixation in situ. Antrum and l:x:ldy I,X>rtions of the glandular stomach were excised and-prepared for electron microscopy. 'll'le thick sections of all specimens were stained with toluidine blue, periodic acid Schiff or alcian blue. Thin sections were observed by transmission electron microscopy. The stomachs from rats administered G-25II intraperitoneally or orally revealed large amounts of mucus in the glandular cells. 'Ibluidine blue stain revealed a substance with high rretachromasia in the pits of stomachs, representing secreted mucus. Periodic acid Schiff am alcian blue stain revealed increased amounts of both neutral and acidic mucus in the glandular cells. Transmission electron microscopy confirrred increased accumulation and secretion of mucus in the stomach with G-25II. Since both oral and intraperitoneal administration induces similar changes in stomachs, direct luminal contact of G-25II with mucus cells is not required. Three days after the last administration, stomachs revealed reduced mucus secretion, rather less than the control stomach. This result suggests that small peptides from Ostertagia specifically enhance mucus production and secretion in rat stomachs ana this action is reversible.

26 NUTRITI

Growing, male Sprague-Dawley rats were subclinically infected with nematodes (Nippostrongylus brasiliensis) and ooccidia (Eimeria nieschulzi) tO produce Single and OOuble infectiOnS • In the 00u0le infectionS 1 the coccidial infection was superimposed on the nematode infection after allowing sufficient time for all nematodes to arrive in the gut. In each experiment there were two control groups: ( 1) uninfected rats fed ad libitum, and (2) uninfected rats pair-fed with each infected ani.ma!':'" Specific (viz., distinct from the effects of anorexia) effects of infections included ( 1) a reduction in feed conversion efficiency in doubly-infected rats, but oot in singly-infected ones~ ( 2) reduction in liveweight gains in the doubly-infected rats, but not in singly-infected ones~ ( 3) a depression in the apparent digestibility of dry matter following the anoretic period in rats infected with ooccidia alone, but oot -18-

in those doubly-infected or infected only with nematodes: (4) a reduction in apparent organic matter digestibility in rats infected with nematodes for one day and for four consecutive days in those infected with coccidia, but no reudction in doubly-infected rats; ( 5} reduction in apparent nitrogen digestibility in doubly-infected rats and those infected with coccidia only, with the occurrence of the concurrent nematode infection being associated with an earlier onset of decreased digestibility and an increase in its duration from two days to five.

27 LIFE CYCLE OF ISOSPORA SUIS OF BABY PIGS W. L. CURRENT, D. s. L!Ni5SAY, Department of Zoology-Entorology, Auburn University, and J. v. ERNST, u.s. Department of Agriculture, Agricultural Research, Auburn, Alabama.

Sporogonous development of Isospora suis of swine was determined using established guidelines. Uninucleate sporonts underwent nuclear division, became binucleate, and then divided to form two round uninucleate sporoblasts. Binucleate sporoblasts elongated to form binucleate sporocysts, each of which then gave rise to four sporozoites. Sporulation was completed with 56 hr at 20 C, 40 hr at 35 C, 16 hr at 30 C, and 12 hr at 37 C. When sporocysts were freed :100ehanically frcm the oocysts and exposed to excysting solution, movement of the sporozoites inside the sporocyst was seen within 5 minutes. Indentations in the sporocyst wall became apparent and total or partial collapse of the sporocyst wall followed. I.rrmediately following collapse of the sporocyst wall, released sporozoites were sluggish but became more active after incubation in excysting solution. 'nle early endogenous development of I. suis was also studied to supplement an earlier report (Lindsay et -al:-;-1980). J. Parasitol. 66: 771-779} which described stages frcm 1.5 to 10 days postinoculatiOn (PI). Sporozoites were seen inside epithelial cells at 10 hr PI. Stages seen at 20 hr PI were sporozoites, binucleate Type 1 meronts and Type 1 merozoi tes indicating that merogony takes place 24 hr earlier than previously described. 'nlis research was supported in part by USDA Grant No. SEA-592011120510 to WLC and by General Cooperative Agreement No. ARS-587830-2-313 between the Alabama Agricultural Experiment Station and the u. s. Department of Agriculture, Agricultural Research.

28 MASSIVE PERI'IOOEAL CESTODIASIS IN A OCG J. F. WILLIAMS, M. C. LINDSAY and P. G. ENGELKIRK, Department of Microbiology and Public Health, Michigan State University, East Lansing, Michigan.

At a routine ovariohysterectomy on a clinically normal 18-month-old Italian Greyhound about 0.5 L of packed cestode larvae 1-10 nun. in diameter were recovered from the peritoneal cavity. The dog remained normal for 2 years until rapid development of a painful and distended abdomen necessitated surgery, at which time overwhelming larval cestode infection was found. Massive abdominal enlargement was associated with parasitic infiltration of all viscera. .Adults of Mesocestoides were present in the intestine. Although light and electron microscopic Characteristics of the -19-

peritoneal fot1ilS, many of which woere cystic and acephalic, woere not typical of those described previously for Mesocestoides, the occurrence of peritoneal larval cestodes and patent intestinal adult infection with this genus suggests that the t~ woere related. Comparisons made with other reported instances of aberrant infections with Mesocestoides and taeniid metacestodes will be discussed.

29 HIS'IOux;ICAL FINDnx;5 IN o:x;s NATURALLY INFECTED WITH HEPA'IOZOON CANIS T. M. CRAIG1, L. P. JONES2 and R. M. N:>RI:GREN'1, Department of Veterinary Microbiology and Parasitology, Texas A&M University 1 and The Texas Veterinary Medical Diagnostic Laboratory2, College Station, Texas.

The diagnosis of infections with Hepatozoon canis in cbgs from the Texas Gulf Coast has been enhanced by identirlcation at various stages of the life cycle in skeletal muscle. Pyogranulomas, merozoi tes, schizonts and a previously undescribed cyst have been identified. Myositis was not apparent in rrost of the biopsies sul::mi tted. 'l.he diagnosis was based on finding thin-walled cysts averaging 250 urn in diameter. 'lhe nucleus ( 15-60 x 30-90 urn) was surrounded by a bluish, mucinous, often granular material and fine laminar membranes which gave the cyst an onionskin appearance. In some cases the cyst nucleus appeared to be undergoing division. Some cases were dlaracterized as a myositis and/or myocarditis with well-defined pyogranulomas oomposed almost equally of macrophages and neutrophils with occasional eosinophils. Very few plasma cells or lymphocytes were found and no giant cells reCClgnized. In one case there was notable sarcolemminal cell proliferation along the edge of the lesion. The lesions in the heart appeared to be rrore diffuse than the skeletal muscle. 'lhere was no evidence of encapsulation of any of the granulomas observed. 'l.he lesions, especially in the myocardium must be differentiated from those of Chaga's disease.

30 CAPILLARIA PO'IORII IN OCJMESTIC CATS J. H. GREVE, Department of Veterinary Pathology, Iowa State University, Ames, Iowa.

Mul t Capi~laria putorii woere found in the gastric mucus of 11 of 60 (18.3%} poUrid cats or pet cats. Female parasites neasured 3.46-7.40 mm, and males measured 2.53-5.29 mm. 'l.he eggs neasured 57-66 x 21-28 m an:i could be differentiated from those of Capillaria aerophila. Nb lesions or clinical signs were attributed to inf'ect1on wi'Eh C. putorii. It was suspected, but not proven, that the nematodes had ooen carrl.ed into the stomachs via intestinal reflux. 'l.his is the first record of c. putorii in domestic cats in North America.

31 CLINICAL OJTBRFAK OF DICTYOCAULUS ARNFIELDI IN FDRSES IN ILLINOIS N. M. COLE, J. A. DiPIETRO, G. J. BAKER, and K. S. '!ODD, JR., College of Veterinary z.edicine, university of Illinois, Urbana, Illinois

In November of 1981, 2 weanling miniature horses were presented to the University of Illinois VMTH with a 2-month history of cyclic fevers and -20-

respiratory infections unresponsive to 5 different antibiotic therapies. Clinical signs of intermittent coughing, bilateral mucopurulent nasal discharge, polypnea, and prominent bronchovesicular sounds throughout the lung fields were observed in both weanlings. Baermann technique on feces from 1 of the weanlings was :pJSitive for D. arnfieldi larvae. Clinical workup on the weanlings :Lncluded complete blood counts, cytology and microbiology culture of tracheal aspirates, endoscopy, thoracic radiographs, and' pubronary ,l';)erfusion scintigraphy. Results revealed secondary bacterial infection and increased radiographic lung densities. Scintigraphy revealed large perfusion defects consistent with abcesses, granulomatous processes, or large infarcts. Verminous bronchitis with secondary bronchopneUJOOnia was diagnosed. Mebendazole ( 20 mg/kg) and trimethoprim-sulfadiazine mixture ( 6. 8 ngjkg) was used to treat both weanlings for 5 consecutive days. ~ weeks after treatment, clinical signs of coughing and nasal discharge subsided. One month after treatment both weanlings were negative for D. arnfieldi. The weanlings orginated fran a herd of 11 miniature horses and 7 donkeys pastured together in central Illinois. In the spring of 1978, 2 donkeys died acutely. A necropsy of 1 of these donkeys revealed subacute, suppurative pneumonia with cross-sections of nematodes indicative of Dictyocaulus sp. In the fall of 1981, a third 3-month-old donkey had an acute respiratory episode and died within 24 hours. 'Necropsy revealed chronic pneumonia. A fecal profile of the remaining horses and donkeys on the farm revealed 3 lungworm positive donkeys. No other miniature horses or donkeys were showing clinical evidence of respiratory disease.

32 COMPARISCN OF QUANTITATIVE FECAL TECHNIQUES m IDRSES J. A. DiPIETRO, K. S. 'lUDD, and N. M. (X)LE, <:bllege of Veterinary Me:dicine, University of Illinois, Urbana, Illinois

Three quantitative and 1 qualitative fecal examination techniques for equine helminth ova were carried out 25 times each. A modified McMaster's technique (MMT) The Cornell McMaster's technique (CMT), a modified Stoll's technique (MST), and a sugar flotation technique (SFT) were used. 'Ihe techniques were compared for variability, differences in mean values, and % positives. Feces used were obtained from the rectum of a 1-year-old horse over a single 2-hour period. All four techniques were 100% positive for strongyles. Significantly (p = .05) different mean strongyle egg per gram counts (EPG) were found using the MMT (3584), CMT (2718), and the MST (650). The coefficient of variation of the strongyle EPG was greatest for the MST (40.2%), less for the MMT ( 30. 9%) , and least for the CMT ( 19. 3% ) • The SFT was 76% positive for . The MST was 52% positive for P. equorum, while £he MMT was 32% and the CMT 16%. Significantly (p = .05) oifferent mean P. a:8}rum EPG were found using the MMT ( 112) than the 01T ( 8. 0) or MS'f" ( • which were similar. 'Ihe coefficient of variation of the P. eqll<.)rum EPG of the CMT (223.0%) was higher than that of the MMT ( 171.6%) andthe MST ( 115.1%). -21-

33 '!HE :roPUIATIOO DYNAMICS OF HElMINTHS OF THE GASTRJNINTESTINAL 'mACT OF OORSES Nr SLAtx:;HTER C. R. REINEMEYER, S. A. SMITH, R.. P. HERD, and A. A. GABEL, '!he Department of Veterinary Pathobiology, 'Ibe Chio State University, Columbus, Ohio. Horses necropsied at the Ohio State University, College of Veterinary Medicine were examined for \\Orms at the rate of 4 per ronth fran May 1 , 1981 to April 30, 1982. Aliquots of stomach, cecal and colonic contents, and pepsin/HCL digests of the stomach and cecal mucosa were examined, and worm burdens quantitated and identified to genus, species, sex and reproductive status. The cyathostomes comprised the majority of the parasite p:>pulation. Five species which have been shown to be resistant to benzimidazole anthelmintics (Cylicocyclus nassatus, Cyathostomum coronatum, Cth. catinatum, Cylicostephanus goldi, and Cph. long~bursatus) made up 66% and 84% or the cecal and colon \\Orm burirens, respectively. Reproductive activity of the small strongyles decreased in September and October, as indicated by a decrease in gravid females and an increase in spent females. An increase in tissue larvae stages in January and February suggested that arrested development is at a peak during these months. The prevalences of large strongyles ( 33%) and mesenteric arterial lesions (35%) were lower than previously rep:>rted. Ascarids, pinworms and cestodes were also relatively uncommon in the adult horses examined.

34 EXPERIMENTAL OCULAR LARVA MIGRANS OOE 'IO BAYLISASCARIS PRCX::YONIS IN SUBHUMAN PRIMATES K. R. KAZACOS, W. A. VESTRE, and E. A. KAZACOS, Departments of Veterinary Microbiology, Pathology and Public Health, and Small Animal Clinics, Purdue University, west Lafayette, Indiana.

The purpose of these studies was to assess the ability of Baylisascaris procyonis to cause ocular larva rnigrans ( OLM) in subhuman prunates, as an indication of its possible zoonotic importance. Four squirrel roonk.eys {Saimiri sciureus) were inoculated ~ .£:! with 5, 000 or 10,000 larvated B. procyon1s eggs, and four cyncm:)"'~fus roonkeys {Macaca fascicularis) received 20,000 eggs.. '!be squirrel monkeys were clinically examined bY direct and indirect ophthalrooscopy at 14 days, and the cynonclgus roonk.eys every 2-3 days p:>stinoculation. All of the monkeys developed fulminating, severe CNS disease; the squirrel monkeys died at 12-19 days and the cynomolgus roonk.eys at 13-22 days. At 14 days a larval granuloma was seen in the retina of one squirrel monkey.. M::>tile larvae, heroc>rrhages, degeneration and inflamnation were seen in the retinas of one cynomolgus roonkey at 7 days. By 11 days, this animal had near-total destruction of the retinas of ooth eyes, and was dead of CNS disease at 13 days. '1\\o of the other three cynom:>lgus nonk.eys had significant ocular lesions by 14-16 days. Histologically, moderate to severe OLM was seen in all of the roonkeys. Ocular lesions consisted of larvae and larval granulomas in the retina and choroid, with various degrees of retinal and choroidal disruption, degeneration, inflanmation arrl heroorrhage. 'Ibese results indicate that Ba;tlisascaris procyonis _has marked capabilities for the production of ocular larva migrans 1n subhuman primates. Based on these results, it is likely that the parasite could produce OLM in human beings in situations where infection took place. -22-

35 CCMPARISON OF THE PERIPARTORIENT RISE {PPR) IN FECAL EGG COONTS OF EXOr!C AND IXMESTIC EWES c. H. COurtney, c. F. Parker, K. E. McLUre, and R. P. Herd, COllege of Veterinary Medicine, Ohio State University, Columbus, Ohio.

Ewes of three exotic breeds (Florida Native, Barbados Blackbelly, and St. Croix) showed no PPR when housed from late fall through lambing and weaning. J):)mes tic breed ewes {Finn Dorset X Rantxmillet) showed a pronounced PPR, while St. Croix X domestic ewes showed an intermediate PPR. No PPR was seem in non-lambing ewes. In a second experiment, differences in the PPR were not as pronounced when ewes were allowed to graze a o:::mtaminated ,PaSture after lambing. Florida Native, St. Croix, and 3/4 St. Croix X 1/4 domestic ewes showed a reduced PPR. 'lbe remaining breeds (Barbados Blackbelly, F1 hybrids of domestic and exotic breeds) showed a higher PPR. 'lbe reduced PPR in the exotic breeds implies less suppression of immunity during lactation compared to domestic breeds, as well as reduced contamination of ,Pastures with '!f.Orm eggs.

36 AN EXPERIMENTAL mDEL OF BREED RESISTANCE 'IO BAEMCNCHUS ())N'IORI'US IN SHEEP c. H. Courtney, C. F. Parker, K. E. McLure, and R. P. Herd, College of Veterinary Medicine, Chio State University, COlumbus, Chio.

An experimental m:Jdel was developed to study breed resistance of domestic and exotic sheep to laboratory infections of H. contortus. Few differences were found between domestic and exotic l5reed lambs after primary infection with H. contortus. Ibwever, when lambs were dewormed after patency, and rEi'-infected one week later, substantial breed differences were found. D:::mestic breeds (Dorset, Rantx:millet, Suffolk, Finn crosses) showed little or no reduction in worm recovery after reinfection as compared to controls receiving a primary infection at he same time. St. Croix lambs showed a 99% reduction in worm burden, whereas Barbados Blackbelly, Florida Native, and 3/4 St. Croix X 1/4 domestic lambs had intermediate worm burdens. In these breeds there was a mixture of "responder" and "non-responder" individuals with worm burdens similar to the St. Croix and domestic lambs, respectively.. Factors such as a;:re, sex, and hemoglobin type are currently being evaluated with this system.

37 EPIDEMIOI.OOY OF BOVINE WNGDR-1 INFECTICN IN WES'I'EFN RAN3E CATrLE D. E. IDRLEY, J. B. WINTERS, R. H. JACOBSON and J. C. FOX, Veterinary Research Laboratory, Montana State University, Bozeman, M:Jntana.

'lbe rovine lungworm (Dictx;;caulus viviparus) as it occurs in Montana is a high prevalence/low intens1ty infection in beef herds moved to summer ranges in late May or early June. Initial exposure in spring-rom calves occurs during their first sunmer on pasture. cnset of patent infections follows a distinct seasonal pattern beginning in July or August arrl persisting until November or December. Spontaneous reactivation of dormant infections appears to take . place on a regular basis in some yearling animals 3 to 5 m::mths after initial calfhood infections beccme nonpatent. -23-

CNerwinter survival of larvae on pasture was found to occur under certain conditions and may be the primary source of exposure to calves during their first grazing season. Wildlife reservoirs (elk, mule deer and llJ.X)Se) may contribute to contamination of summer ranges but are not l:elieved to l:e an important factor in maintenance of bovine infections.

38 HElMINTHS OF CA'!TLE IN WYOMING: 1961 AND 1977 R. C. BERGSTroM and B. A. WERNER, Division of Microbiology and Veterinary Medicine, University of Wyoming, Laramie, Wyoming.

TWo surveys of trichostrongylid nematodes of cattle have been completed in Wyoming. The first survey (1957-61) included 375 calves, 228 yearlings and 275 mature beef cattle. After a sixteen year interim the second survey was made which included 676 calves, 431 yearlings and 383 mature cattle. Mean eggs per gram did not change significantly in calves ( 14 and 20 ep:J), in yearlings (29 and 19 ep:J) or in adult bovines (22 and 21 ew) • 1\b significant trends were discernible.

39 OBSER\TATIOOS OF OSTERI'AGL2\. OSTERTAGI J?OPUIATIONS IN TRACER CALVES GRAZED WITH BEEF YEARLil'I3S J. c. WILLIAMS, I K.. s. MARBURY,, B. A. BA.UMANN1 I T. G. ~IDER1, Department of Veterinary Science 1 and Department of Veterinary Pathology3, :u:>uisiana State University, Baton Rouge, I.auisiana, J. W. Kf:>DX2 and M. D. KIMBLE2, Ped River Valley Experiment Station2, :u:>uisiana State University, Bossier City.

Use of experimental tracer calves in epidemiological research on gastrointestinal nematodes of ruminants is expensive and demanding of resources. Ibwever, data furnished on oorm population dynamics in relation to events in permanently grazed cattle can l:e obtained by no other rreans. Tracer calves, raised free of helminth infection to 5-7 months of age, were grazed at tronthly intervals with yearling beef cattle during 1981 in northwest Louisiana. SOme examples of these observations are given. Tracers grazed during November through February acquired few to no inhibited 0. ostertagi; the expected increase in inhibited larvae was seen from February Efirougfi April and numbers declined in May. Adult 0. ostertagi predominated from N:>vember through February. Tracers grazed on-a pasture ~n April, which had been free of animals for 2 months, had considerably lower worm burdens than tracers grazed on continuously contaminated pasture. TWo additional April tracer calves, confined and treated repeatedly with thiabendazole or levamisole, had substantial o. ostertagi infections at 78 and 141 days after reroval from pasture. In ~ tracers grazed during May and treated weekly while at pasture, o. ostertagi burdens were reduced slightly1 all other genera TNere considerably reducea. Two tracers TNere grazed during August on a pasture which was freed of cattle on July 1. Numbers of Haaronchus and Cooperia spp. were substantially reduced. -24-

40 CRYP'IDSPORIOOSIS UPDATE B. C. ANDERSON, University of Idaho, caldwell Veterinary Teaching Center, Route 8, Box 267, caldwell, Idaho.

frYEtos:poridium appears to be gaining attention as a significant animal pathogen. This coccidian infects numerous species including avian, reptilian and mammalian (including domestic animals and man). The significance in animals is related to the probable high incidence in beef and dairy calves. The infection is often mixed with enteric viral infections and the combination appears to be severe to lethal. The effects of pure Cryptosporidium infection in calves may be minimal unless complicated bY other enteric pathogens, p:JOr management, undemutri tion and/or inappropriate antibacterial therapy. The long term effect on production p::>tential has not been evaluated. The public health significance of cryptosporidiosis will have to be evaluated. Interspecies transmission of the infection has been demonstrated experimentally, including man to animal transmission. In addition, cases in people that have recently been in contact with Cryptose::ridium-infected calves, have been documented. Furthermore, fatal cases in i.mmunocompromised humans have been recognized. The veterinary profession needs to be fully informed on cryptos:poridiosis.

41 SYMPOSIUM: THE BIQr..o:;y OF CRYPIDSPORIDIUM: CRYP'IDSPORIDIOSIS IN HUMANS AND CALVES w. L. CURRENT, and N. c. REESE, Department of Zoology-Entomology, Auburn University, Alabama. Cryptos:poridiosis was diagnosed and rroni tored in 12 heal thy individuals who had direct contact with animals from 3 separate, unrelated outbreaks of calf cryptosporidiosis. Clinical symptoms included diarrhea arrl abdominal cramping for 3 to 12 days. Two of the cases were asymptomatic. All of the human cases were diagnosed by the presence of Cryptosp::>ridium sp. oocysts in the feces. The derronstration of oocysts in f:ecal rlotations has proven to be a reliable technique for diagnosing and rronitoring cryptosporidiosis. Therefore, histologic examination of intestinal biopsies from human subjects or of intestinal tissues obtained from animals during necropsy is not necessay for diagnosis of this disease. Fecal samples were obtained from 3 :i.rrmunodeficient humans with persistent cryptosporidiosis who had undergone repeated intestinal biopsies in order to noni tor their infections. Large numbers of oocysts were dem:>nstrated in their fecal samples, and this technique is now being used to nonitor these infections. O:Jcysts of human and of calf origin were norphologically indistinguishable, and produced similar infections in suckling mice, rats, and previously uninfected calves. 'lhese data sup:port the view that cryptos:poridiosis is a and that calves with diarrhea are a potential source of infection. End.ogenous developnent of ~tosp::>ridium was investigated in three-day-old white mice inoculatedorally with oocysts isolated from a calf. Two mice were necropsied at 4, 8, 12, and 16 hr p::>stinoculation (PI) and then 2 mice were necropsied every 24 hr from day 1 through 9 PI. S:porozoites were observed in mucosal scrapings of the -25-

obtained 4, 8, 12 and 16 hr PI. Trophozoi tes, i.rrmature schizonts, and mature schizonts with 8 merozoites were seen in small intestinal tissues by 16 hr PI. Mature schizonts observed in mucosal scrapings, 1-mn-thick plastic sections, and in thin sections prepared for transmission electron microscopy (TEM) contained 8, 6, or 4 merozoites. Sexual stages were present in small intestinal tissues obtained days 4-9 PI. TEM revealed that all endogenous stages were in a parasitophorous vacuole within rrodified microvilli. Schizonts, macrClg'ametocytes, and micrClg'ametocyt.es could be distinguished by TEM. SporClg'ony occurred within the rost tissues which resulted in oocysts containing 4 sporozoites and a large residuum. Ultrastructure of endogenous stages of the calf isolate of Cryptosporidium will be compared with that of isolates from inmunologically noiiiial ara imnunodeficient humans. 'Ibis research was supp:>rted in part by General Cooperative Agreement No. ARS-587830-2313 between the Alabama Agricultural Experiment Station and the u. S. Department of Agriculture, Agricultural Research.

42 MINOR USE IN DROOS w. A. Knapp, Paleigh, North carolina. The number of new drug entities approved by FDA for use in food animals during the last 15 years has been considered by many to be quite low. Since 1974, for instance, the average annual approval rate has approximated 1. 5 new drug entities for the major species of livestock, i.e. cattle, swine, and p:>ultry. '!he minor species of food animals (sheep, goats, rabbits, ducks, gamebirds, and foodfish), have recieved no new drug entity approvals since 1964. 1m overview, including an historic perspective as well as an assessment of current activities to increase the approval rate for ooth major and minor species of focd animals will be presented.

3 REPORI' OF MEETIN:; - NO ABSTRACT 44 REPORI' OF MEETING - ID ABSTRACT

45 REPORI' OF MEETIN:; - NO ABSTRACT

46 REPORI' OF MEETING - ID ABSTRACT -26-

4 7 IDENI'IFICATION OF ANIMAL PARASITES IN TISSUE SECTICNS: A NEW Sl'UDY SET AVAilABLE AT THE AFIP C. H. GARDINER, Department of Veterinary Pathology, Armed Forces Institute of Pathology, Washington, D. c.

A new study set is available at the Armed Forces Institute of Pathology and stresses identification of metazoan animal parasites in tissue section. '!he set is comp::>sed of a syllabus, 83 microslides and 313 Kodachromes. '!he syllabus is comp::>sed of three sections. '!he first section details how to identify a parasite; the second describes the microslides; and the third describes each Kodachrome. Kodachromes have been prepared from each slide and illustrate the characteristic morphologic features of each parasite. '!he set may l::e used for teaching and/or for reference. Sets may be !:arrowed for a maximum of 2 weeks by writing: '!he Director, AFIP, Washington, D. C. 20306.

48 THE EFFECI' OF IVERMECTIN CN TRANSMISSICN PATI'ERNS OF EQUINE INTESTINAL NEMA'IODES K. G. I:l.Jili!G and T. M. CRAIG, Department of Veterinary Microbiology and Parasitology, J. M. &WEN, Large Animal Clinic, Texas A&M University, College Station, Texas. This investigation was designed to provide information on the effectiveness of ivermectin as a means of rontrol of equine intestinal nematodes and on aspects of the epidemiology of equine strongyles as it applies to central Texas. Six mares ~Nere treated with approximately 0.2 mgjkg ivermectin at parturition. '!he mares and their foals were placed on parasite-free pastures. Another six mares were administered a similar amount of vehicle on the day of parturition. 'lhese mares and their foals were placed in an adjoining pasture and served as rontrols. Fecal egg counts from the mares indicated that ivermectin significantly reduced patent infections of equine stongyles for a period of four months. Pasture larval p:>pulations were also reduced. Data from foal fecal egg rounts and necropsies indicated that the treatment of mares with ivermectin at parturition reduced small strongyle burdens in the foals for at least the first five months of life. 'file results ronfirmed that the mare is the most i:m:p:")rtant source of infection for Strongyloides westeri and small strongyles to the foal. The epidemiology of equ1ne strongyles in Texas is different from that reported in Great Britain. '!he mare will pass strongyle eggs year round. No distinct late spring/early summer rise in mare fecal strongyle egg counts was noted, but a distinct mid-summer rise did occur. '!his high egg output coincided with the driest, hottest period of the year when pasture larval counts were low. A reservoir of infective strongyle larvae was created on pasture and with the first autumn rains, there was a dramatic increase in the number of larvae on forage. '!he small strongyle larvae burden in a foal necropsied after the increase in pasture larval rounts was significantly higher than in those foals necropsied l::efore the rise in pasture larval rounts. -27-

49 EFFICACY OF IVERMECTIN AGAINST curANEOUS CNCHOCERCIASIS IN OORSES R. P. HERD and J. c. OONHAM, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio Forty horses showing microfilariae of Onchocerca cervicalis in association with dermatitis, alopecia and pruritus of tEe ventral midline were given a single intramuscular injection of 0. 2 mg/kg of ivermectin in June - August, 1981. Microfilarial o::>unts in 40 horses ranged from 18 - 42,446 microfilariae per skin snip on the day of treatment and histopathologic examination of skin sections showed a chronic eosinophilic dermatitis. There were large numbers of microfilariae in the dermis, but there was no consistent relationship between the presence of microfilariae and the severity of the inflamnatory reaction. In all 40 horses, a marked clinical improvement occurred 2-3 weeks posttreatment, when the lesion was replaced by healthy skin and new hair. Skin snips taken 4-33 days post­ treatment were negative for microfilariae in all 40 horses. When further samples were taken from 15 horses 4-9 months later, 9 of them were still free of microfilariae and the other 6 had low counts {17-97). An additional 7 clinically affected horses, treated in November/December, 1981, when there was negligible chance of reinfection posttreatment were all free of microfilariae at both 6-10 days and 4-5 months posttreatment. This result suggests that ivermectin may be an adulticide as well as a microfilaricide. An edematous reaction occurred on the lower abdomen of 4 {10%) horses and within the area of the lesion in 6 {15%) horses 24 hours post­ treatment. The reactions disappeared after a further 24-72 hours. These 10 (25%) horses had significantly higher pretreatment umbilical microfilarial counts than the 30 horses with no posttreatment reaction. The reaction was attributed to liberation of toxic disintegration products following death of massive numbers of microfilariae. The marked clinical irrprovement in all 40 horses 2-3 weeks after killing microfilariae with ivermectin suggests that microfilariae are involved in the etiology and pathogenesis of the dermatitis.

50 IVERMECTIN IN INJECTABLE AND PASTE EORMUIATICNS: EFFICACY AGAINST FOORrH STAGE STRONGYWS VUlGARIS LARVAE AND POSTTREATMENr RESPCNSES OF PONIES T. R. KLEI, B. J. 'IORBERr, M. R. CHAPMAN, and B. S. KRAMER, Departments of Veterinary Science and Veterinary Microbiology and Parasitology, Louisiana State University, Baton Rouge, Louisiana.

The efficacy of ivermectin at 0.2 ng/kg Cbse level in paste and injectable formulations was tested against eight-week-old Strongylus vulgaris fourth-stage larvae. Infections were intrcduced by per os inoculations of 500 third-stage larvae in parasite-free foals. Using carparisons of dead and viable s. vulgaris recovered 5 weeks post­ treatment, in treated and nontreatea controls, toth formulations were shown to be >99% effective. weight gains were greater in treated foals. Arterial lesions in treated p:>nies were markedly reduced or absent at necropsy. 'lbtal WBC counts, neutrophil numbers and eosinophil numbers were -28-

significantly decreased in treated p::>nies, following treatment. Antibody titers as measured by an ELISA method did not change following treatment.

51 THE EFFICACY OF IVCMOC AGA.INSI' DEFMA'IDBIA Ii<:*1INIS IN CATI'LE R. A. R:lNCALLI and C. BENITEZ-USHER, Merck Sharp and D:>hme Research Laboratories, Rahway, New Jersey.

'.ttle combined results of four trials concluded in Paraguay and Brazil show that iverrnectin* given subcutaneously as a single injection at a dose rate of 200 meg/kg of body weight elicited - 7 to 11 days following treatment - an efficacy of 100, 93, and 99% respectively, against the first, second and third larval stage of Dermatobia haminis in cattle.

* IVOMEC

52 ACARICIDAL ACTIVITY OF IVERMECTIN AGAINST AN EXPERIMENTAL INFESTATIOO OF PSOROPTES OVIS IN CATTLE D. L. FERGU-soN and T. C. SWIECZKCWSKI, Department of Veterinary SCience, University of Nebraska-Lincoln, Lincoln, Nebraska.

'!he avermectins are a new class of fermentation products which have exhibited excellent activity against a wide range of nematodes, insects, and arthropods. The purified components have shown even greater activity. This study was conducted to investigate the acaricidal activity of the B1a component of the avermectins (ivermectin) against experimental infestations of Psoroptes avis in cattle. Eighteen Hereford calves ranging from 350 to 450 lbs were experimentally infested with Psoroptes avis arrl randomly allotted to three groups at 42 days p::>stinfestation: ( 1 ) control (n = 6); (2) 200 meg iverrnectin/kg body weight once by subcutaneous injection (n = 6); and (3) 200 meg ivermectin/kg body weight once orally in a paste formulation (n = 6). Severity of mite infestation for each calf was determined by skin scrapings 9, 4, and 2 days prior to treatment. Each calf was examined at 7 days p::>sttreatment and 7~ay intervals up to day 56 for the presence of Psoroptes avis. Data have teen assembled and will re presented. - Supported in part by a grant from Merck & Co., Inc., Rahway, N.J. 07065. Published as Paper Number 82-1769, Journal Series, Nebraska Agricultural Experiment Station.

53 CES'IOCIDAL ACTIVITY OF FENBENDAZOLE IN CALVES H. CIORDIA, J. A. STUEDEMANN, and H. C. MCCAMPBELL, U. S. Department of Agriculture and the University of Georgia College of Agricultural Experiment Stations, cattle Parasites Research Laboratory, Experiment, Georgia.

Forty-five commercial-grade Angus calves naturally infected with tapew:>rms (M:lniezia sp) were used in 2 controlled experiments to evaluate the cestocidai efticacy of 3 dose levels of fenberrlazole, methyl-5- (phenylthio)-2-benzimidazolecarbamate. In the first trial, 15 calves were divided into 3 groups of 5 each. cne group served as nonmedicated -29-

controls. Other groups were drenched with fenbendazole at dose rates of 10 and 15 :rrg/'.reg of lxdy weight. 'Ihirty calves used in the second experiment were divided into 3 equal groups. cne group served as nonmedicated controls and the other 2 groups •Here drenched at dose rates of 7. 5 and 10 :rrgjkg. Calves were necropsied 12 days after treatment. roses of 10 and 15 :rrgjkg were 100% efficacious in reducing the m.nnber of tape-worm scolices, and a dose of 7. 5 :rrgjkg was 91.7%. Medicated cattle did not show signs of intoxication.

54 CLINICAL TRIALS WITH COMBINATIONS OF MEBENDAZOLE l!.ND PIPERAZINE IN IDRSES J. A. DIPIETRO, A. PAUL, K. S. 'IDDD, College of Veterinary Medicine, University of Illinois, Urbana, Illinois.

Clinical trials were done on 40 horses of various sex, breed, and age with naturally-acquired parasitic infections. 'Ihe h:>rses were selected from a herd that had a history of routine de-worming with benzimidazoles resulting in incomplete activity against strongyles. Prior to the onset of the trial, in vitro testing of the horses for renzimidazole-resistant strongyles was positive. 'Ihe h:>rses were randomly assigned 1 of 4 treatments (Tx): Tx1-8.8 rngjkg mebendazole (MBZ), Tx2-8.8 mgjkg MBZ and 55 :rrg/kg piperazine base (PZ), Tx3-8.8 mg/kg MBZ and 40 mgjkg PZ, and Tx4-8. 8 :rrgjkg MBZ and 25 rngjkg PZ. A 3. 33% suspension of MBZ and a 34% solution of piperazine ronohydrochloride were utilized. 'Ihe treatments were administered once via stomach tube. Fecal samples were obtained from the rectum immediately prior to treatment and 7 days posttreatment. Strongyle egg p:r gram counts (SEPG) using a llOdified McMaster's technique and fecal cultures for third-stage strongyle larvae were done on the samples. 'Ihe oorses were observed for ciiverse reactions throughout the trial. Horses treated with MBZ alone had the smallest geometric mean % , reduction in SERi, 78.2%. A 99.9%, 99. 7%, and 99.7% reduction in geometric mean SEro occurred in the horses in Txs 2, 3, and 4, respectively. Results of fecal cultures prior to treatment indicated that the oorses in all treatment groups were infected with large and small strongyles. Results of fecal cultures 7 days p:>sttreatment indicated that small strongyles were present in oorses treated with MBZ alone {Tx1) rore frequently than oorses treated with MBZ-PZ mixtures. Mixtures of MBZ and PZ appeared to re rore effective in the control of strongyles than MBZ alone. Adverse reactions were rot observed in any of the h::>rses.

55 PROPHY'LAXIS OF roRCINE COCCIDIOSIS WI'!H SALIOOMYCIN T. J. KENNEDY, AEF Research Inc. , waunakee I Winconsin, and J. E. SHIVELY, Pfizer, Inc. Terre Haute, Indiana.

Coccidiosis is emerging as a serious disease in the swine industry. National surveys have shown a 60% prevalence of coccidia in sows, while numerous investigators have described clinical disease in neonatal swine. Because treatments appear to be of little value in coccidiosis, numerous products have been tried as prophylactic routines in the sow. Pigs fed salinomycin at levels of 0.025, 0.05 and 0.1 mgjkg of the diet had fewer -30-

days and lower peaks of oocyst production, improved fecal scores, greater weight gain and better feed conversion than infected nonmedicated pigs.

56 SIGNIFICANCE OF PARASITE STAGE CN PERCEIVED ANTHI.MINTIC EFFICACY AGAINSI' ImKWORM INFEcriON IN IXX;S T. A. MILLER, wellcome Research Laboratories, Kansas City, Kansas.

The three that infect the dogs, Ancylostana caninum, Ancylostoma braziliense and Uncinaria stenocephala, induce hypoprote1nem1a, and hypoalbuminemia through an 1ncreased exogenous catabolic rate of plasma albumin. Ancylostana caninum also causes serious blood loss and is the major hookworm pathogen oi dOgs. The initiation of hypoalbuminemia, and, in A. caninum infection, anemia is related to the interval .PQStinfection and-"V.Urm stage(s) present. When dogs are presented to a veterinarian for treatment for hcx:)kworm infection or disease, the presence of only adult "V.Urms can l:::e detected; coexisting immature pathogenic stages cannot be clinically detected. Pups infected with large burdens of A. caninum can die of acute anemia in the prepatent period still with negat1ve fecals. Clinical differential diagnosis to determine the species of hookworm(s) is difficult. In hookworm-enzootic areas and under sui table climatic conditions, infection and accumulation of hookworm burdens are continuous processes. Hence burdens comprise spectra of age, stage, and in some areas also species of hookworm. It is essential, therefore, that treatment of the hookworm infected dog, particularly in acute anemic animals, be targeted at all stages and preferably also against all species. Of the available canine anthelmintics, few have FDA-approved claims of efficacy against immature worms and all three species.

57 THE EFFECI' OF XANTHENE DYES CN BOVINE GASTROINTESTINAL NEMA'IDDES J. A. HAWKINS, J. R. HEITZ, M. C. HEALY, and M. H. JOHNSON, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi

A previous re:port indicated that erythrosin B was shown to be extremely toxic to third-stage larvae of various gastrointestinal nematodes of cattle. Experimental studies continue to confirm this re:port. Naturally-infected calves of approximately six rronths of age were treated per os with 20, 30, 40, and 60 mg/kg of erythrosin B daily for various periods of time. Untreated calves served as controls. Feces was collected daily prior to and during the treatment period. Fecal cultures were set up and third-stage larvae were collected and exp:>sed to a controlled light source. The effect of days posttreatment and days in culture on the toxicity of erythrosin B to third-stage larvae were investigated. Additional studies were designed to determine the effect on adult nematodes. Preliminary evidence, however, indicates that neither adult nematode viability or fecundity seems to l:::e significantly reduced when calves are treated per os with erythrosin B. There also seems to be little effect on egg hatchability. This is not surprising since the primary toxicity is a light dependent reaction. The comparative toxicity of a -31-

number of different xanthene dyes other than erythrosin B was also determined. Data collected to date continues to support the reported toxicity of erythrosin B to parasitic gastrointestinal nematodes of cattle. Additional studies are planned to further investigate the p::>tential of this group of compounds for use in controlling parasites of domestic animals.

58 EFFICACY OF FENBENDAZOLE AGAINST MIGRAT:rn:i ASCARIS SUUM LARVAE IN PIGS T. B. STEWART and T. D. BIDNER, Department of veteri'ri'a'ry Microbiology and Parasitology and Department of Animal Science, Louisiana State University, Baton Rouge, Louisiana.

Twenty-four cross-bred, weanling pigs were each given 10, 000 embryonated Ascaris suum eggs by mouth. 'Ihe pigs were assigned to three equal groups b¥ sex, ~ht and litter. Group I pigs were individually fed fenbendazole {3rrg/kg) on days 2, 3, and 4 after infection; Group II pigs were individually fed fenbendazole {3rrgjkg) on days 6, 7, and 8 after infection; and Group III pigs were not treated. All pigs were necropsied 24 days after infection and examined for lesions and parasites. Treatment of pigs at either time was effective in reducing the number of A. suum at necropsy by more than 99% when a:>mpared with controls {means: t-; o-:5'1II, 0.1; III, 120.9). rate treatment was nore effective than early treatment in reducing number of liver lesions. Early-treated pigs, rowever, gained weight faster and were nore efficient in conversion of feed into l:x:xiy weight than late-treated or control pigs (means: I, 0.99 and 3.51; II, 0.90 and 3.72: III, 0.73 and 4.06). INDEX '10 AUTHORS

Author Abstract # Author Abstract #

Anderson, BC 40 D:mvres, FW 22

Armstrong, J::lA Dubey, JP 23

Bailey, WS 46 Engelkirk, PG 28

Baker, GJ 31 Ernst, JB 27

Baumann, EA. 39 Ewanciw, DV 21

Bell, RR 3 Farrell, CJ 6

Benitez-Usher, c 51 Ferguson, DL 52

Bergeron, JA 23 Fetterer, RH 9

Bergstrom, RC 38 Foryet, WI 10

Binder, 'ID 58 Fox, JC 37

Blair, LS 21 Frandsen, JC 26

Bowen, JM 48 Gabel, AA 33

Bradley, RE 2 Gardiner, Cli 47

Cerro, JE 17 Giambrone, JJ 12

Chapnan, MR 50 Greve, JH 30

Ciordia, H 53 Grieve, RB 19

Cole, NM 31, 32 Hanmerberg, B 25

Conroy, GA 5 Hawkins, JA 57

Corkum, KC 7 Healey, r.t:: 57

Courtney, Cli 35, 36 Heitz, JR 57

Craig, 'I'M 29, 48 Herd, RP 33, 35, 36, 44, 49

Current, WL 27' 41 Hugh-Jones, M 7 DiPietro, JA 31, 32, 54 Jacob, L 21 oonham,JC 49 Jacobson, RH 37 INDEX 'IO ADTHORS

Author Abstract * Author Abstract # Jen, m 15 McClure, KE 35, 36

Johnson, MH 57 McCraw, BM 16

Jones, LP 29 Miller, TA 56

Kadhim,JK 4 Nordgren, RM 29 Karns, PD 5 Parker, CF 35, 36

Kazacos, FA 34 Patton, s 20

Kazacos, KR 34 Paul, A 54

Kennedy, TJ 55 Reinemeyer, CR 33

Klei, TR 50 Rew, R 9

Klesius, PH 12 Rhodes, MB 13 Knapp, WA 42 Rikihisa, y 25

Knox, JW 39 FDncalli, RA 51

Kramer, BS 50 Sand, RS 2

Lauria, s 19 Schillhorn Van veen, 'lW 14

Lindemann, EA 24 Schlotthauer, JC 5, 18

Lindsay, DL 27 Scholtens, R 20

Lindsay, M: 28 Shively, JE 55 Loyacano, A 7 Slocombe, o 16 LUdwig, KG 48 Smith, SA 33

Malatesta, PF 21 Snider, 'IG 39

Malone, JB 7 Staudinger, LA 13 Marbury, KS 39 Stewat, TB 58

McCall, JW 24 Stromberg, BE 5, 18

M.cC~ll, HC 53 Stuedemann, JA 53 INDEX 'IO AUTHORS

Author .Abstract # Author .Abstract t

Swieczkowski, ~ 52 Wescott, m 6, 15 'Iheodorides, VJ 11 Williams, JC 39 Tcxld, KS 31, 32, 54 Williams, JF 28, 43

Torbert, BJ 50 Winters, JB 37 Urban, JF 22 W::>rley, DE 37 vestre, WA 34 Zirnmerman, GL 8, 17, 45

Werner, FA 38